Automatic mapping system



Aug. 25, 1953 Filed Sept. 5, 1947 D. H. CLEVVELL.

AUTOMATIC MAPPING SYSTEM 2 Sheets-Sheet 1 ATTOR EY g- 1953 D. H. CLEWELL 4 AUTOMATIC MAPPING SYSTEM Filed Sept. 3, 1947 2 Sheets-Sheet 2 BYQ: 4

ATTO EY Patented Aug. 25, 1953 UNITED STATES PATENT OFFICE AUTOMATIC MAPPING SYSTEM Application September 3, 1947, Serial No. 771,997

Claims. (Cl. 33-4415) This invention relates to systems for automatically tracing the course of a vehicle on a map carried by it so that the position at any time, or the path of prior movement, of the vehicle Fig. 6 is a plan View of parts appearing in Fig. 5; and

Fig. '7 shows a balanceable network comprised in the system of Fig. 5.

may be ascertained by inspection of the map. 5 Referring to Fig. 1, the earth-inductor coil l0 Though not limited thereto, the system is suited is continuously rotated by a motor ll suitably for installation on a car or truck used in mounted in fixed position with respect to the geophysical prospecting so that data obtained frame of the car, truck or other vehicle whose in the field may be correlated with definite course is to be traced or recorded on a chart or geographical positions or so that the vehicle may 10 map. The Co l i9 is 50 located as to be substanproceed expeditiously, even cross-country, to detially clear of, or unaffected by, magnetic matesired geographical locations within large areas e-l 01 dev c W th forming p Of e to be explored for potential oil-bearing formavehicle or its equipment: the direction of the tions. flux line of the earths field in the vicinity of coil In accordance with the invention, the earths If! should correspond with the true direction of magnetic field is utilized to produce an alternatthe earths field in the gen neighborhood o ing current signal used to maintain fixed the the car or vehicle. orientation in space of one movable element of A coil l2, rotated continuously in syhchrohism a system. A second element of the system is with coil I0, is disposed in the field of a magnet movable in accordance with the linear distance l Which for Simplicity y comprise p pieces traveled by the vehicle, the two elements jointly 5 S t y attached to a p a t bardetermining and varying the relative position magnet The @0115 I0 and 12 y be mounted of the map and an associated stylus during on the shaft of motor I I, but if necessary to avoid progress of the vehicle, effect of local stray fields the coil W may be In accordance with one f rm of th invenlocated at another more favorable position of tion, the alternating signal is produced by an the vehicle and the necessary synchronism beearth inductor compass; whereas in other forms tween rotation of the coils obtained by a Selsyn of the invention the alternating current signal arrangemen r eq v l rv y mis produced by afiux-gate compass. In all forms As the coils l6 and I2 rotate respectively in of the invention, the phase relation of the signal the a t c fi d 0f the rth a f th a produced by the inductor compass, magnet I3, they each produce an alternating current netometer, or equivalent with respect to a second VOItage AS own by curve E1 of Fig. the alalternating current signal is used to control the ati voltage produced y e 0011 iii each position of a directional element effective to s maXime s the ho ontal aXiS of the coil resolve the linear travel of the vehicle into its Ves through 0u P s tion and has its north-south and east-west components, minima as the axis of the coil passes through the The invention further resides in systems haveast-West positions, and this is u ardless ing the features of combination and arrangef h heading of the Vehicle. ment hereinafter described and claimed. Assuming the moment t t the net !3 For more detailed understanding of the inis at rest W h espect to the Vehicle, the phase vention and for illustration of preferred forms of e alternating Current O put of coil 2 With thereof, reference is made to the accompanying respect t0 the Phase f the alternating e t drawings in which: output of coil l0 depends upon the heading of the Fig. 1 schematically illustrates the essential Vehicle. y y Of eXemple, assuming e horimechanical and electrical components of an uzontal axes of the coils Ill and I2 are in the same tomatic mapping system using an earth-inductor Vertical plane, and a Particular Dolihg 0f the compass; coil connections, the alternating outputs of the Fig. 2 is an explanatory figure referred to in Coils l0 and i2 may be Out of p e Whe discussion of Fig. 1; the field between the pole tips 14 and i5 of mag- Fig. 3 schematically shows a phase-discriminan I3 is parallel to the earths field and has the tor network usable in the system of Fig, 1; same polarity, that is, the north poles of the two Fig. i is a modification of Fig. 1 using a fiuxfields are on like sides of the coils l0 and [2. This gate compass; 180 phase relation of the two voltages is shown Fig. 5 is a modification of Fig. 4 using another by curves E1 and B(Ez) of Fig. 2. When the magtype of magnetometer; net I3 is parallel to the earths field but with reverse polarity, the two output voltages of the coils Hi and i2 are in phase, as shown by curves E1 and A(E2) of Fig. 2. For each other intermediate angular position of the magnet it, there is a corresponding unique phase relation between the two output voltages, the output voltage E2 of coil 52 leading or lagging the output voltage E1 of coil is in dependence upon the sense of relative displacement of the magnet 13 with respect to the earths field, and the extent of the phase difference of the outputs being a function of the extent of the angular displacement'of'magnet it.

The two alternating voltages E1 and E 2 are impressed upon a phase-discriminator H of any suitable type, whose output is' utilized to control a motor is which is suitably coupled as by gears l9, 2% and 2| to effect rotation of the magnet it about the rotational axis of coil 52. When, for example, the two voltages E1 and E2 are 180 out of phase, the output of the phasediscriminator H is essentially zero, and motor is remains at rest. So long as the vehicle heading remains that for which the voltages are out of phase, the magnet it therefore remains in fixed predetermined position in space with respect to the earths field. As soon, however, as the heading of the vehicle is changed, there is a shift in phase between the two voltages E1 and E2 and motor [8 is energized to return the magnet !3 to its predetermined angular position with respect to the earths field corresponding with null output of the discriminator. It is not essential that the discriminator ill be of a type which has zero output when the input voltages are 180 out of phase: it is only necessary that the discriminator output be zero for a particular or unique phase-relation of the input voltages corresponding with a fixed position in space of the magnet I3 and a predetermined fixed angular relation between the horizontal axes of the coils iii and 12.

Because the voltage output of the pickup coil it is inherently small, it is desirable to magnify it before impressing it on the phase-discriminator if. The amplifier 22 interposed between the coil it and the phase-discriminator if for that purpose may be of any suitable type well known in the electronic art and uses a suitable number of amplifier stages to attain the desired high gain. include peak-limiting or clipping arrangements, or is operated under saturated conditions affording inherent clipping action, so that the wave form of the voltage E1 as impressed upon the phase-discriminator is essentially that of a pulse having steep sides so to afford increased sensitivity of the discriminator to shifts in phase, and will be independent of variations in the magnitude of the voltage induced in coil iii.

The output voltage of the coil I2 may be, and preferably is, also amplified and clipped as by amplifier 23 in order that the two voltages E1 and E2 as applied to thediscriminator network i! may be of the same amplitude and wave form.

In resetting the magnet E3 to its normal or reference position in space, the motor is also actuates a direction element 2i which, as more fully hereinafter explained, is effective in resolving the linear travel of the vehicle into its north-south and east-west components. In the preferred arrangement shown the directional ele ment 24 supports a wheel or roller 25 rotated in accordance with the linear progress of the vehicle. The roller 25 may be directly coupled to a Wheel of the vehicle, but is preferably mounted The high-gain amplifier 22 should 4 4 upon the shaft of a servo-motor 26 electrically connected to servo-generator 21 in turn mechanically coupled to one of the wheels of the vehicle or to an auxiliary trailer wheel. In any event, the rate of rotation of the wheel 25 cor responds with the speed of the vehicle, and the number of its revolutions over a given period of time therefore corresponds with the distance traveled by the vehicle during that time. For clarity, the roller or wheel 25 is consequently designated as the distance element of thie; mapping system.

The direction element and the distance element are. jointly used automatically to effect, during travel of the vehicle, corresponding changes in the relative position of a map and an associated stylus 37 which may serve as an indicator, or a marking element, or both.

In the preferred construction shown, the driving wheel 25 frictionally engages a platform 23 to the upper surface of which is suitably attached a map or chart to be moved with respect to stylus 31. The platform 28, as viewed in Fig. l, is free to move to the right or to the left, but is precluded from rotating or moving in any other direction by guides 29 extending upwardly from a second platform 30 which, as viewed in Fig. 1, is free to move into and out of the plane of the paper. Platform 36 is precluded from moving in other directions by the guides 3l-3l which may be integral with the frame 32 of the apparatus. Preferably, the platform 30 rests upon a plurality of anti-friction rollers 33, or equivalent, spaced along a shaft 34 extending between the guides 3!. There are a plurality of such shafts, suitably spaced and each having a group of spaced rollers 33, to permit the platform 30 freely to slide to and fro between the guides 3|. Similarly, the platform 28 rests upon a series of groups of anti-friction rollers 35, each group of rollers being spaced along a shaft 36 extending between the guides 29 for platform 28.

When the horizontal axis of the direction member 24 is parallel to the longitudinal axis of platform 28, and therefore normal to the corresponding axis of platform 30, rotation of wheel 25 is effective to move the platform 30 in direction normal to the plane of the sheet, Fig. 1. Under this circumstance, the platform 28 and platform 3E! both move with respect to the vehicle, but there is no change in relative position of the two platforms. Conversely, when the axis of the direction element 211 is at right angles to the position shown in Fig. 1, the rotation of the wheel 25 is effective to move the platform 28 to the right or left and with'respect to platform 30 which remains at rest. For other positions of the direction element 24, the motion of the vehicle with respect to geographic north-south line is resolved into two mutually perpendicular components, and both platforms 28 and 33 move with respect to each other and with respect to frame 32 in accordance with the magnitudes and senses of those components. Consequently the f geographic position of the vehicle may at any time be ascertained by looking at the relation between the map and the associated stylus 3'! carried by the frame 32; in addition, and assuming the stylus 3f is a marking element, the path taken by the vehicle is traced upon the map.

As an example of a phase-discriminator network suited for controlling the positioning motor 88 in accordance with phase relations of the Voltages E1 and E2 of coils it and i2, reference is made to Fig. 3. One of the voltages, voltage E1 for example, may be impressed upon the primary winding of a transformer 38 whose output terminals are connected through a rectifier bridge or demodulator network 39 to the coil system 49 of a relay 4!. The other voltage, specifically voltage E2 in the example assumed, is impressed upon the primary winding of a transformer 42 whose secondary terminals are respectively connected to taps of the secondary winding of transformer 38 and the coil 40 of relay 41. The rectifiers of the bridge 39 are so poled that when the voltages E1 and E2 are in phase, direct current flows through one of the coils of relay 4|; whereas when they are 180 out of phase, the current flows through the other coil of relay 4!. Th armature 43 of the relay 4| therefore defiects in on direction or the other from its neutral position selectively to energize one or the other of the field coils 44-45 of motor 18 to effect its rotation in proper direction to restore the magnet 13 to the position corresponding with average null or balanced output of the discriminator 17. With this particular discriminator arrangement, there is null effective output when the voltages E1 and E2 are 90 out of phase as the currents in relay coils are effectively in balance; accordingly, if the mechanical portion of the apparatus is so designed that the reference position of the magnet I3 is the north-south position, the horizontal axes of the coils m and 12 should be at right angles to each other. If they are parallel to each other, this type of discriminator may be used provided a 90 phase shifter is interposed between it and the source of one or the other of the voltages E1 and E2.

In the modification shown in Fig. 4, components having the purpose and function of components appearing in Fig. 1 are identified by like reference characters. In general, only those components not appearing in Fig. 1 are hereinafter specifically discussed.

In this modification, one winding of the motor ISA for positioning the directional element 24 is energized by the output of an amplifier 22A upon which is impressed the alternating voltage produced by a flux-gate compass 41 supported upon the shaft 48 of gear 2|. The other winding of motor 18A is energized from the alternating current source 45: through the frequency-doubler 52 which may be of any suitable type. The compass comprises a core structure 49 of suitable magnetic alloy, such as Mumetal, Permalloy, or the like, whose alternating flux permeability is substantially affected by unidirectional flux having field strength of the same order as that of the earth. The percentage composition of suitable lviumetal may be approximately 75% nickel, iron, 5% copper and small percentages of manganese, chromium, silicon and/or other elements. The coil 50 of the compass is energized with alternating current, from the alternatingcurrent source 45, whose peak values are sufficient to saturate the core. The pickup coils 5| of the magnetometer are connected in series to provide an input voltage for the amplifier 22A. The frequency of this voltage is twice that of the source 43; any fundamental frequency component of the output of coils 5| is greatly attenuated by the filter 53 interposed between the compass and the amplifier.

When the horizontal axis of the core member 49 is normal to the earths field, the component of the earths field along the core is zero and the voltage output of the pick-up coils 5|, 5! is zero. Under this circumstance, only one winding of .uration earlier in those half-cycles.

motor I8A is energized and it therefore remains at rest. For other angular positions of the core member 49, a component of the earths field is resolved parallel to the magnetically saturable axis of core member 49. For angular positions in one direction from normal, the above component of the earths field will add to the flux from coil 50 during alternate half-cycles of the exciting voltage applied thereto and cause sat- This unbalances the coupling to pick-up coils 5l--5l, and a second harmonic signal is developed which is in-phase with the output from frequencydoubler 52 and which phase is representative of the particular sequence of half-cycles in which the fiux from the earths component aids the flux from coils 5i-5l. For angular positions in the other direction from normal, flux addition and earlier saturation of core member 49 occur during the oppositely polarized sequence of alternate half-cycles. The resulting unbalance again develops a second harmonic signal in coils 5l5l, but this signal is out-of-phase with the first-developed signal, and hence out-of-phase with the voltage from frequency-doubler 52. The double-frequency output of the pick-up coils 5|, 5!, applied to one winding of the motor i8A after amplification, is of magnitude increasing with increasing deviation of the core member from normal position and is in-phase or out-of-phase with respect to the output voltage of the frequency-doubler 52, applied to the other winding of motor ISA, in dependence upon the sense of the deviation.

Motor 18A is a two-phase type whose direction of rotation is determined by the phase relation of the alternating voltages respectively applied to the two-field windings and productive of a magnetic field rotating in one direction or the other in dependence upon the phasing of the field-excitations. Hence, the rotor of motor ISA will discriminate in its motional response between field-excitation voltages that are in-phase and out-of-phase, performing the function of a phase-discriminator plus the function of a motor.

Consequently as the vehicle in which the system is mounted moves along and takes various headings, the compass member 49 is maintained in an east-west position under control of the reversible two-phase motor ISA which is effective, concurrently with its re-setting adjustments of member 49, to move the direction member 24 for control of the relative position of the map and stylus 31.

The modification shown in Figs. 5, 6 and 7 is similar to that of the preceding figures, particularly Fig. 4. In this modification, the detector element for producing an alternating current of phase and magnitude determined by the angular position of the element with respect-to the earths field comprises a pair of wires 55, 5B, of a suitable alloy such as Mumetal, whos alternating current resistance is a function of their angular position with respect to the earths field. The two wires are suitably mounted on a supporting structure 51 for rotation by shaft 48, Figs. 5, 6, and are electrically connected for inclusion in a balanceable electrical network 58 which may be a Wheatstone bridge including, as other arms, the resistors 59, 69 of metal whos resistance is substantially unaffected by the earths magnetic field.

The input terminals of the network are connected to the source 46 of alternating current and the outputof the network, preferably after amplification by amplifier Z2 oi? any suitable type, is impressed on the phase-discriminator.

As the structure 57 rotates from its normal position, Fig. 6, to increase the-angle between one of the wires 65, 56 and the earths fieldF and concurrently to decrease the angle between the other of the wires and the earths field F, the alternating current resistances of the wires are differentially changed to unbalance the network 68 in-sense dependent upon the direction of rotation of member 67 from normal position.

Accordingly each time the vehicle heading is changed, the motor 18, under control .of the phase-discriminator 17A, returns the member .57 to its normal position in space, corresponding, of course, to anew position with respect to the vehicle, and actuates the direction member 24 for the same purpose as in the modifications previously described.

It shall be understood the invention is not limited to the particular arrangements described, but that changes and modifications may be made within the scope of the appended claims.

What is claimed is:

1. In an automatic system for effecting relative movement between a stylus and a map support to indicate the position of a vehicle and to trace its course, an azimuth-sensitive detector, circuit elements and a controlled element energized by said detector in response to azimuthal motion thereof with respect to the earths field rotationally to orient'said detector and said controlled element on a predetermined azimuth heading, 2. wheel mounted on said controlled element with a diameter of said wheel substantially coincident with the axis of rotation of said controlled element and with the plane of said wheel aligned with said predetermined azimuth heading, and a motor mounted on said controlled element continuously to drive said wheel in accordance with forward and reverse motions of the vehicle, said wheel being coupled to the map support to drive it in radial motion about the axis of'said controlled element on the azimuthal heading determined by said detector, whereby a polar-coordinated plot of the vehicles position and course of movement is produced.

2. A mapping arrangement as in claim 1 in which the azimuth-sensitive detector comprises a magnet and a pair of coils rotatable in synchronism, one in the field of said magnet and the other in the earths field; and in which the circuit elements energized by the detector comprise a phase-discriminator upon which the alternating current outputs of said coils are impressed, and a motor controlled by the output of said discriminator to maintain for different headings of the vehicle a predetermined fixed relation of said magnet to the earths field.

3. Amapping'arrangement as in claim 2 which additionally includes an amplifier-clipper in circuit with said detector and said discriminator for efiecting similarity of the amplitudes and waveforms of th outputs of said coils as impressed upon the discriminator.

4. A mapping arrangement as in claim 1 in which the azimuth-sensitive detector comprises abalanceable network including resistors whose alternating current resistance varies as a function of their angular-position with respect to a unidirectional magnetic fiux,.structure for supporting said resistors for rotation in the earths field, anda source of alternating current connected to the input terminals of said network; and in which the circuit elements energized by the detector comprise a phase-discriminator connected tosaid source and upon which is also impressed any unbalanced output of said notwork, and a motoncontrolled by the output of said discriminator for maintaining fixed, notwithstanding difierent headings of the vehicle, the position of said structure with respect to the earths field.

5..A mappingarrangement as inclaim 1 in which the azimuth-sensitive detector comprises a flux-gatemagnetometer mounted for rotation in the earths field anda source of alternating current for energizing 'theexciting coils of said magnetometer, and in which the circuit elements energized by thedetector comprise a phase-discriminator connected to saidsource and upon which isalso impressed the output of the pickup coils of saidmagnetometenand a motor controlled by the output of said magnetometer for maintaining fixed, notwithstanding difierent headings of the vehicle, the position of said magnetometer with respect to the earths field.

DAYTON H. CLEWELL.

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